Crank case



FIG. 1 is a perspective view of a crank case showing the design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a side elevational view thereof; and,

FIG. 7 is a side elevational view of the opposite side thereof.

The ornamental design for a crank case, as shown and described.